1. Field of the Invention
The present invention relates to fabric bulk bags. More particularly, the present invention relates to a novel bulk bag configuration wherein the bottom of the bag has an octagonal or other multi-sided shape which, when filled with product, is fully supported by the pallet without the bag needing to shift and lean. As a result, the side walls stay naturally in position. This bag is more attractive and much safer to stack upon.
2. General Background of the Invention
In the art of making bulk bags, the historical designs have all been created from the point of view of manufacturing efficiency. The goals have been to eliminate waste and reduce manpower.
Hence, almost all bulk bags have been made with square or rectangular bottoms with vertical walls rising up from the four sides. A good example of this would be the original designs of Peter Nattrass, one of the early inventors of the bulk bag concept.
This concept eliminates any lost fabric and makes production quite efficient with straight sewing lines in all major seams.
However, in usage, a bulk bag is simply a box shaped flexible fabric container. As loose product is poured into the bag, it applies equal pressure in all directions. Uncontained loose product when poured onto the ground forms a cone with a circular shaped bottom. When this natural action is applied to product entering into a fabric bag, the natural forces attempt to change the bag into a cylinder.
In the lower portions of the bag, this cannot occur as the fabric that is directly attached to the square bottom is held to that configuration. But the further up the vertical walls of the bag from the bottom, the less control the bottom square has over the side wall fabric. Within the first 10 inches (25 cm) of the vertical sidewalls above the bottom square panel, the shape of the bag becomes cylindrical. The constraints of the square bottom no longer applies. The flexible bag forms a nearly perfect cylinder in the central portions of the filled bulk bag.
The perimeter of the bag becomes the circumference of the cylinder. Bulk bags come in a variety of sizes. The most common are 34 inches (86 cm) square, 35 inches (89 cm) square, 36 inches (91 cm) square, 37 inches (94 cm) square and 38 inches (97 cm) square.
For purposes of discussion we will use the 37 inch (94 cm) square bag for all the following discussions but it is clear that this new design can be applied to all sizes of bags by using the same thought processes described below.
A bulk bag that is made 37 inches by 37 inches (94 cm by 94 cm) square has a perimeter of 37 inches (94 cm) times 4, or 148 inches (376 cm). A cylinder with a 148 inch (376 cm) perimeter has a diameter of 148/Pii (3.1416) or 47.1 inches (120 cm) in diameter.
Therefore a filled bulk bag that started out as a 37 inch (94 cm) square bag has a square bottom of 37×37 inches (94 cm×94 cm) and an area of 1369 square inches (8832 square cm). Approximately 7 to 8 inches (18 to 20 cm) above the floor the bag has rounded out to a cylinder with a diameter of 47.1 inches (120 cm) and a cross sectional area of 1742 square inches (11,238 square cm).
The resulting cylinder has an area that is greater than the base by 27.2%. This then leads to the conclusion that approximately 25% of the product within each standard bulk bag design is initially unsupported by the pallet or floor. This means that each side of the square bottom bag has unsupported columns of product that are greater than 6% of the total product.
Since the bag has no supporting structure, the loose product outside the support area of the floor or pallet will shift downward during the vibration of handling.
This movement will continue until the great majority of the product within the bag has reached a supported position.
Since the diameter in this case is 10 inches (25 cm) larger than the cross section of the base, the only way for the product to reach support is to convert a portion of the bag sidewall into a floor. In other words, 5 inches (13 cm) of sidewall will be laid flat to gain the support for the product in the 25% of unsupported cylinder that was described above.
If this happens evenly all around the bag, then the bag simply becomes approximately 5 inches (13 cm) shorter with a cylindrical shape from the floor or pallet to the top of the product area.
However, with any inertia such as happens with transport, the product settles to the floor more quickly in one direction versus the other directions. In this case, the product will lay more than 5 inches (13 cm) horizontally to that one side to reach support. This natural action then results in causing the bag to lean in that same direction. One side is longer than the opposite side so the bag is forced to lean toward the newly shortened side.
This is the basic cause of the instability that most bulk bags exhibit when being shipped or being stacked.
The only known exceptions to this are bulk bag designs called baffle bags and some bulk bags that are made with a fully circular bottom. In the case of baffled design bags, the main body of the bag has interior walls that prevent the bag from reshaping itself into a cylinder. While this is an option, it is a fairly expensive option that requires extra fabrics and extra sewing seams. Further, it separates the interior of the bag into 5 separate chambers. The baffle bag essentially tries to overcome the natural forces of gravity by force.
The proposed invention in this patent is attempting to work with the natural forces by providing a more natural rounding to the bag base.
The other known prior art are bags that have a circular bottom, for example, from Japan. While this bag is very stable, it is difficult to place on a square pallet. It has no straight sides to help the operator line up the edges. Further, the 47 inch (119 cm) diameter bag would have to be on a minimum 47 inch (119 cm) square pallet for full support. Since export containers are only 92 inches (234 cm) wide, 2 pallets of this side cannot fit into the containers side by side. Therefore, the bag will have areas of non-support that droop down over the edge of the necessarily smaller pallet and be vulnerable to damage. The invention proposed here eliminates this particular issue with the fully circular bottom bag.
However, after 30 years of International recognition, this design has not moved successfully into the rest of the world. This has been primarily because of the expense and difficulty of producing this design.
In producing the same bag spoken about above, the perfect circle of 47.1 inch (120 cm) would have to be created from a minimum of a 51 inch (130 cm) square piece of fabric. The bottom panel on a bulk bag is a supporting panel and thus generally involves at least one fold of fabric to create two layers at all points of the seam. This means that the bottom requires a piece of fabric with an area of 2,601 square inches (16,781 square cm).
The bottom for the same bag in standard square design is made from 42×42 inches (107×107 cm) fabric with an area of 1764 square inches (11,381 square cm) of fabric. Therefore, the circular bottom requires 47% more fabric than the bottom of the square bag.
In a production situation, the sewing machines used in this industry are designed for straight line sewing. It is quite difficult for this type of machine to apply a seam in a circular manner. The operator must sew only an inch or two (3 to 5 cm) then stop and turn the fabric slightly. This happens approximately 74 times on this type of bag. This number of stops makes the cost of labor go up and the speed of production goes down.
Therefore, there is a need in the industry to provide a bag which will be stable when filled, yet which will be easy to construct without creating wasted fabric or slows down production, as does round bags. The present invention, which is a bag having an octagonal bottom, solves those problems. By going to an octagonal bottom, we speed up the sewing, reduce the waste, fit pallets and provide an appearance that is not square but also not round, which provides a larger footprint when the bag is filled to avoid the side walls of the bag from making contact with the surface upon which the bag rests and causing the filled bag to sag and being unable to support filled bags stacked on top of it.